The presence of essential functional groups with a suitable spatial arrangement for chelation with metal ions of enzymes is a significant feature common to several classes of antibiotics [Moshfegh, A. et al. Helv. Chim. Acta 1957, 40, 1157]. They include trisaspidinol [Widen, C.-J. et al. Helv. Chim. Acta 1973, 56, 831], cryptosporin [Closse, A. et al. Helv. Chim. Acta 1973, 56, 619], and tetracycline [Albert, A. Nature (London) 1953, 172, 201]. These compounds exhibit various degrees of activity against Gram-positive bacteria as well as other microorganisms. It was reported that the presence of halogen atoms in phloroglucide analogs is essential for their antibacterial activity [Hakimelahi, G. H. et al. Helv. Chim. Acta 1981, 64, 599; Swiss Patent 003848, 1977; Swiss Patent 003849, 1977; Swiss Patent 007448, 1978. Moshfegh, A. A. et al. Helv. Chim. Acta 1982, 65, 1221; Helv. Chim. Acta 1982, 65, 1229; Helv. Chim. Acta 1982, 65, 1264].
.beta.-Lactam antibiotics exert certain biological activity by acylating serine residues of transpeptidases, in which the cross-linking of peptidoglycans does not take place [Waxman, D. J. et al. J. Biol. Chem. 1980, 255, 3964]. The ring opening of the .beta.-lactam nucleus would occur when cephalosporins react with bacterial enzymes. Consequently, the substituent attached at the C-3' position is liberated. When the eliminated species possesses antibacterial activity, cephalosporins would exhibit a dual mode of action [O'Callaghan, C. H. et al. Antimicrob. Agents Chemother. 1976, 10,245; Greenwood, D. et al. Antimicrob. Agents Chemother. 1976, 10, 249; Beskid, G. et al. Chemotherapy 1990, 36, 109]. It was reported that attachment of antibacterial quinolones to the C-3' position of cephalosporins gives a class of new compounds with a broadened spectrum of antibacterial activities [Albrecht, H. A. et al. J. Med. Chem. 1990, VI, 77; J. Med. Chem. 1991, 34, 669; J. Med. Chem. 1994, 37,400].